1. Field of the Invention
The present invention relates to an organic electro-luminescence device, and more particularly, to an electro-luminescence device, having data lines, gate lines and voltage supplying lines formed from materials that are different from each other and corresponding to each function, and capable of enhancing its characteristics, and to a method of fabricating the same.
2. Discussion of the Related Art
Recently, there has been an increased requirement for a flat panel display device having a small possessory space independent of an enlarged display device. An electro-luminescence device is at the forefront of the flat panel display devices.
The electro-luminescence device is divided into an inorganic electro-luminescence device and an organic electro-luminescence device in accordance with the material used.
The inorganic electro-luminescence device conventionally applies a high electrical field to a light-emitting portion in order to emit light. The high electrical field accelerates electrons and allows the accelerated electrons to be impacted, thereby exciting a light emitting center. During excitation of the light emitting center, the inorganic electro-luminescence device emits the light.
The organic electro-luminescence device injects electrons from a cathode and holes from an anode into a light-emitting portion to transfer excitons from an exciting status to a base status, thereby emitting light. The electron and holes, which are injected into the light-emitting portion are combined to form the exciton.
The inorganic electro-luminescence device having the operation principle as described above requires a high voltage of 100 to 200 volts as a driving voltage because of the application of the high electric field to the light-emitting portion. The organic electro-luminescence device has an advantage that it is driven by a low voltage of about 5 to 20 volts. In light of this point, the organic electro-luminescence device is actively developed.
Also, the organic electro-luminescence device is used for a picture element (or a pixel) of a graphic display, a television image display or a surface light source, owing to its characteristics of wide viewing angle, high-speed response and high contrast. Furthermore, since the organic electro-luminescence device is thin and light and provides a high chrominance, it is adapted for a next generation flat panel display.
FIG. 1 shows an organic electro-luminescence device including gate lines GLl through GLm and data lines DLl to DLn arranged to cross each other on a glass substrate 10, and picture elements PE arranged at each crossing of the gate lines GLl to GLm and the data line DLl through DLn.
When a gate line on the gate line GLl to GLm is enabled, each picture element PE is driven to generate light corresponding to a video signal on the data line DL.
In order to drive the electro-luminescence device, a gate driver 12 is connected to the gate lines GLl to GLn and a data driver 14 is electrically coupled to the data lines DLl through DLn. The gate line 12 sequentially drives the gate line GLl through GLm. The data driver 14 applies video signals to the picture elements PE through the data lines DLl to DLn.
The picture elements PE driven by the gate driver 12 and the data driver 14 each include an electro-luminescence cell OLED connected to a ground voltage line GND and a cell driving circuit 16 for driving the electro-luminescence cell OLED, as shown in FIG. 2. The cell driving circuit 16 is connected between the electro-luminescence cell OLED and the ground voltage line GND.
Referring to FIG. 2, the cell driving circuit includes a second PMOS TFT (P-channel Metal Oxide Thin Film Transistor) T2 connected between the electro-luminescence cell OLED and a supply voltage line VDD to drive the electro-luminescence cell OLED, and a first PMOS TFT T1 connected between the data line DL and a gate electrode of the second PMOS TFT T2 to switch the picture signal to be applied to the gate electrode of the second PMOS TFT T2, and a capacitor Cst connected between a drain electrode of the PMOS TFT T1 and the supply voltage line VDD.
In explaining an operation of the cell driving circuit in association with a driving waveform diagram of FIG. 3, the first PMOS TFT T1 is turned-on when a low input signal, i.e., a scanning signal from the gate driver 12 is applied to the gate line GL. If the first PMOS TFT T1 is turned-on, a video signal received synchronously with the scanning signal from the data line DL flows through the first PMOS TFT T1 and is charged into the capacitor Cst. The video signal has a predetermined amplitude.
The capacitor Cst connected between the drain electrode of the first PMOS TFT T1 and the supply voltage line VDD charges the video signal applied from the data line DL while the low input signal is supplied to the gate line GL. The capacitor Cst holds the video signal, which is applied from the data line and charged thereinto, during one frame. The holding operation of the capacitor Cst enables the application of the video signal from the data line DL to the electro luminescence device OLED to be maintained.
An organic electro-luminescence device having such a configuration of the picture element PE requires a number of data lines adapted for receiving each image signal such as R(Red), G(Green), B(Blue), etc.
FIG. 4 is a circuit diagram showing another configuration of the conventional picture element PE. The picture element PE of FIG. 4 includes an electro luminescence cell OLED connected to a ground voltage line GND and a cell driving circuit 26 positioned at a crossing of a data line DL and a gate line GL. The cell driving circuit 26 is connected between the electro luminescence cell OLED and the data line DL.
The cell driving circuit 26 includes a third and fourth PMOS TFT T3 and T4 forming a current mirror between the electro luminescence cell OLED and a supply voltage line VDD; a fifth PMOS TFT T5 connected between the data line DL and the gate line GL to respond to a signal on the gate line GL; a sixth PMOS TFT T6 connected between nodes of gate electrodes of the third and fourth PMOS TFTs T3 and T4, the gate line GL and the fifth PMOS TFT T5; and a capacitor Cst connected between the node of gate electrodes of the third and fourth PMOS TFFs T3 and T4 and the supply voltage line VDD.
FIG. 5 explains an operation of the picture element shown in FIG. 4. The fifth and sixth PMOS TFTs TS and T6 are turned-on if a low input signal is applied to the gate line GL. When the fifth and sixth PMOS TFTs TS and T6 are turned-on, a video signal received synchronously with the scanning signal from the data line DL is charged into the capacitor Cst through the fifth and sixth PMOS TFTs T5 and T6. The video signal has a predetermined amplitude.
The capacitor Cst between the node of the gate electrodes of the third and fourth PMOS TFTs T3 and T4 charges the video signal from the data line DL while the low input signal is applied to the gate line GL. The capacitor Cst holds the video signal, which is applied from the data line DL and charged thereinto, during one frame. The holding of the capacitor Cst allows the application of the video signal from the data line DL to the electro luminescence cell OLED to be maintained.
An organic electro-luminescence device having such a configuration of the picture element PE requires a number of data lines adapted for receiving each image signal such as R(Red), G(Green), B(Blue), etc.
The video signal, which is charged into the capacitor Cst and held during one frame, is applied to the electro luminescence cell OLED so that an image (or a picture) is displayed on a display panel.
FIG. 5 is a plan view showing the construction of the gate line and the data line of the organic electro-luminescence device in FIGS. 2 and 4 crossing each other.
Referring to FIG. 5, there are data lines DL and supply voltage lines VDD arranged alternatively in the horizontal direction and gate lines GL arranged in the vertical direction.
In the case of an organic electro-luminescence device of a VGA mode having picture elements of 640xc3x97480, the gate lines GL of 480 columns are formed in the vertical direction. The data line and the supply voltage line VDD are alternatively formed in the horizontal direction of 640 rows, for displaying a mono picture. For a color picture, lines of 3840=640xc3x973xc3x972 are formed in the horizontal direction because of the requirement of having the data lines and the supply voltage lines for each R, G and B picture element.
As described above, since a density of the lines in the horizontal direction is higher than that of lines in the vertical direction as the number of lines in the horizontal direction is more than those in the vertical direction, there is a disadvantage that a stress increases in the horizontal direction.
The organic electro-luminescence device also radiates heat during the emission of light, thereby being continuously heated at about 70xc2x0 C. Due to this, the breaking of wires at the crossings between the wires (or the crossings between the lines) is increased.
FIGS. 6A through 6D explains a step-by-step method of fabricating a gate line, a data line and a supply voltage line of a conventional organic electro-luminescence device.
Referring to FIG. 6A, a metal layer 36 is first deposited on a substrate 34 in order to form each line of the organic electro-luminescence device. The metal layer 36 is formed from a conductive material such as aluminum or an alloy of aluminum by a sputtering process, for example.
On the metal layer 36, a photo resist pattern 38 is formed as shown in FIG. 6B. The photo resist pattern 38 is produced by a process of uniformly coating a photo resist on the metal layer 36 to a desired thickness, exposing the photo resist to ultraviolet rays using a photo mask (not shown) arranged thereon, and developing the exposed photo resist by a developing solution. At this time, the exposed photo resist is subjected to ultraviolet rays, which changes the molecular structure so that it is dissolved into a material soluble by the developing solution.
The metal layer 36 exposed by the photo resist pattern 38 is etched using an etching process, such as a wet etching, using the photo resist pattern 38 as an etching mask. The metal 36 has a pattern the same as the photo resist pattern 38, as shown in FIG. 6C. In the case where the metal layer 36 is etched by a wet etching, an etchant such as an aqueous solution of (NH4)2S2O8 is used, for example.
The photo resist pattern 38 on the metal layer 38, which is not etched, is removed by stripping equipment after the etching process, as shown in FIG. 6D.
In such a conventional electro-luminescence device, a liner expansion in the wiring is enlarged by the heat because aluminum or an alloy of aluminum having a low resistance is used to deposit the metal layer 36. Due to this, the conventional electro-luminescence device has a disadvantage that the breaking of wiring is increased. The conventional electro-luminescence device also has another disadvantage that a crossing of two wires is broken by a chemical reaction with an etchant used to etch one of the wirings, because various wirings are formed from the same material.
Accordingly, the present invention is directed to an electro-luminescence device that substantially obviates one or more of the problems due to the limitations and disadvantages of the related art.
An advantage of the present invention is to provide an organic electro-luminescence device that is adapted to improve its characteristic by using materials different from each other and corresponding to each function for a formation of data lines, gate lines and supply voltage lines, and a method of fabricating the same.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the organic electro-luminescence device according to one aspect of the present invention includes: a plurality of gate lines for receiving scanning signal; a plurality of data lines for receiving data signal; and a plurality of supply voltage lines arranged alternatively with the data lines, wherein at least one of the gate line, the data line and the supply voltage line is a wiring formed from a metal material having a high melting point.
The metal material having a high melting point is any one of chromium, manganese, molybdenum, tungsten and tantalum.
The gate line, the data line and the supply voltage line are formed from a material different from each other.
The gate line is formed from a material having a high melting point that is high in a thermal stability.
The supply voltage line is formed from a metal having a low resistance characteristic.
The data line includes a conductive layer formed by a material different from those of the gate line and the supply voltage line.
The metal of the low resistance characteristic is any one of an alloy of aluminum and a double structure of aluminum and a metal of high melting point.
In another aspect of the present invention, the method of fabricating the organic electro-luminescence device having a plurality of gate lines for receiving scanning signal, a plurality of data lines for receiving data signal and a plurality of supply voltage lines arranged alternatively with the data lines includes: forming a conductive layer for at least one of the gate line, the data line and the supply voltage line, the conductive layer including a metal material having a high melting point.
The forming of the conductive layer includes: depositing the metal material having a high melting point on a substrate; forming a photo resist pattern on the metal material; patterning the metal material using the photo resist pattern as a mask to form a signal wiring on the substrate; and removing the photo resist pattern.
The conductive layer forms conductive layers for the gate line, the data line and the supply voltage line, the conductive layers formed from materials different from each other.
The conductive layer for the gate line includes the metal material having a high melting point.
The conductive layer for the supply voltage line is formed from any one of an alloy of aluminum and a double structure of aluminum and a metal having a high melting point.
The conductive layer for the data line is formed from a metal material having a high melting point different from those of the gate line and the supply voltage line.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.